Pulse circuits



March 15, 1949. R. PROSKAUER 2,464,259

PULSE CIRCUITS Filed May 11, 1944 c CATHODE TIME-v VOLTAGE F|G.3 V U U, TIME r VOLTAGE FIG.5

INVENTOR RICHARD PROSKAU ER Patented Mar. 15, 1949 UNITED STATES PULSE CIRCUITS Richard Proskauer, Westbury, N. Y., assignor to The Sperry Corporation, a corporation of Delaware Application May 11, 194 i, Serial No. 535,069

2 Claims. 1

My invention relates to circuits for electric discharge devices and concerns, particularly, pulse generating circuits.

An object of the invention is to provide a source of electrical impulses in which pulses may be obtained in periodically recurrent groups of two or more pulses.

A further object of the invention is to provide a multiple-pulse blocking oscillator.

Other and further objects, features and advantages of the invention will become apparent as the description proceeds.

In one embodiment of the invention, a blocking oscillator circuit is employed in which a parallel tuned circuit is connected in the cathode lead instead of connecting the cathode directly to the negative terminal of the power supply.

A better understanding of my invention will be afforded by the following detailed description considered in conjunction with the accompanying drawing, and those features of the invention which are believed to be novel and patentable will be pointed out in the claims appended thereto.

In the drawing,

Fig. 1 is a circuit diagram of one embodiment of my invention;

Figs. 2, 3 and 4 are graphs illustrating the principle of operation of the apparatus of Fig. 1; and

Fig. 5 is a circuit diagram of a modified embodiment.

The apparatus illustrated comprises an electric discharge device such as a vacuum tube H, a pulse transformer 2|, a tuned circuit or tank circuit l3 and a power supply M, represented for convenience as a battery of cells. The tube ll includes conventional electrodes, namely, an anode l5, a control electrode or grid l6 and a cathode IT. The tank circuit l3 includes a condenser l8 and an inductance I9. The pulse transformer 2| includes a winding l2 connected in series with the tube H between the positive terminal of the power supply [4 and the anode l5, 2. second winding 22 connected to the grid circuit of the tube II, and if desired also a third winding 23 serving as an output winding.

For providing a return to a voltage above cutoff, a grid leak resistor 24 is connected between the positive terminal of the power suppl I l and the grid For coupling the grid to the grid winding 22 of the pulse transformer 2 I, the winding 22 is connected at one end to the positive terminal of the power supply It and is coupled at the other end through a coupling condenser 26 to the grid It. If desired a throttling resistor 25 may be provided. In th arrangement illustrated it is connected in series with the coupling condenser 26.

The period of the tank circuit [3 is made considerably shorter than the period of the blocking oscillator with this tank circuit short circuited, in order that oscillations may be produced having a higher frequency than the blocking oscillator pulses which would normally be produced by the blocking oscillator without the tank circuit l3.

The wave forms of the voltages appearing at the plate, the cathode and the grid of the tube l I are illustrated in Figs. 2, 3 and 4, respectively.

It will be understood that in a normally operating blocking oscillator circuit, the grid I6 is alternately driven positive to render the tube H conductive and driven strongly negative beyond cut-off to render the tube non-conductive. Since the grid I6 is returned to a voltage above cut-off by the grid leak 24 the grid it always tends to drift in the positive direction, but as soon as the potential difference between the grid and the cathode becomes less than the cut-oil? voltage, the tube H becomes conducting, a pulse of current flows through the winding l2 and abruptly induces a voltage in the winding 22. The polarity of the induced voltage is such as to drive the grid [6 more strongly positive, attracting electrons from the cathode to the grid, whereby a strong charge is built up upon the condenser 26 which eventually biases the grid l6 negative and holds the tube II in a cut-off condition during the period between current pulses. The presence of the tuned circuit l3. however, results in higher frequency oscillations taking place whenever the tube 1 I has been rendered non-conducting by the negative charge on condenser 26.

The behavior of the circuit appears to be as follows: During the re atively long cut-off time between groups of h gher frequency oscillations or pu ses. the blocking oscillator tube II is in nonconducting condition. During this time the grid is held at a voltage beow cut-off by a charge built up on the grid condenser 25. The tube begins to conduct when the voltage on the grid condenser has been reduced by leakage of its charge through the grid leak 24 to such a point that the potential difference between the cathodeand the grid is equal to the cut-off voltage of the tube, as

illustrated in Fig, 4. The grid voltage gradually rises along the line 3! until it reaches cut-off at the point 32.

When plate current conduction begins, as in the normal blocking oscillator circuit, a voltage is induced in the grid winding 22 of the blocking oscillator transformer by the rate of change of plate current. This change is of such polarity that the grid is driven further positive and a current rapidly builds up to a saturation value as in other blocking oscillators. Just as in other blocking oscillators, when the plate voltage has fallen to substantially that of the cathode and there is no further rate of increase in current, the induced voltage in the winding 22 falls to zero. The pulse is cut off since the grid current flow during the conducting period has charged the grid condenser 26 to a voltage considerably in excess of the cut-ofif voltage.

The role of the tank circuit i3 appears to be as follows: Owing to the high inductance of the choke coil l9, no appreciable-current is built up through it during the brief conduction period. The charge moved during thepulse, therefore, comes from the condenser l8 causing its ungrounded plate l8a to become positive. At the conclusion of the initial pulse, the condenser I8 is left With the positive charge and the tank circuit 13 then oscillates at its free natural 'frequency. Owing to the fact that the tube II has been cut off, it does not tend to damp out this oscillation.

The free oscillation of the tank circuit upon cut-off of: the tube causes the voltage of the oathode with respect toground to undergo sinusoidal excursions as illustrated in Fig. 3. At successive times when the cathode is falling in potential,

the tube conducts again owing to the fact that the decreasing cathode potential results in the grid becoming less negative with respect to the cathode. The cut-on condition'depends upon the potential difference between the grid i6 and the cathode l1, rather than upon the actual Voltage of the gri'df'lffi with respect to ground. The number of successive pulses which take place is limited by the voltage across the grid condenser 26, which builds up witheach pulse until the negative voltage on thegrid exceeds the negative voltage which can be reached'by the cathode by an amount larger than thecut-ofi bias of the tube I l.

Whenever the cathode voltagereaches the lowerlimit'value and permits current tofiowthrough the tube H, an additional voltage pulse is induced in the grid winding 22, so that the grid voltage also'fiuctu'ates at the frequency of the cathode voltage. However, after a sufiicient cumulative grid current has flowed to charge the grid co-ndenser'iifi, the grid voltage'falls sharply along the line 3'4 (Fig. 4'), driving'the tube to cut-01f and no further conduction takes place until the grid voltage has risen along the portion 3i of the grid voltage curve to the/grid voltaget-Z.

By adjusting the rheostat 30, the number of oscillations produced in each group may be adjusted so that the circuit may be employed for producing a-series of pulses at a frequency considerably higherthan the frequency of oscillation which would? be produced by the time constant of the grid circuit: and an effect may be produced corresponding to high frequency pulses with blanks of adjustable length between groups of pulses.

On theaother handif the trigger pulse generator 35 has'a frequency equalling the desired repetition rate for groups :of pulses, the accuracy ofrepetition rate is determined thereby and the frequency of "the induced oscillations is determined by the resonant frequency of the tuned circuitl 3. In'this case the grid I6 ma be biased to-substantially cathode voltage without risking frequency drift.

Although the tuned circuit l3 has been shown connected in the anode-cathode circuit of the tube ll, it will be understood that my invention is not limited to the specific arrangement shown. In the case of a multi-electrode tube the tuned circuit may be connected in the circuit of another suitable electrode. For example, in the case of a pentode as illustrated in. Fig. 5, the tuned circuit may be connected in the screen grid circuit.

I have herein shown and particularly described certain embodiments of my invention and certain methods of operation embraced therein for the purpose of explaining its principle of operation and. showing its application, but it will be obvious to those'skilled in the art that many modifications and variations are possible, and I aim, therefore, to cover all such modifications and variations as fall within the scope of my invention which is defined in the appended claims.

What is claimed is:

1. In combination, an electric discharge device having an anode, a cathode and a control electrode, a pulse transformer with a. first Winding connected in series with the anode and a grid winding connected at one end to the first winding, a grid leak resistor connected to said control electrode, a coupling condenser and a damping resistor connected in series with the remaining end of the grid winding and the control electrode, a resonant tank circuit connected in series with the cathode of the electric dischar e device, and means connected to said first winding for applying to said anode and said control electrode a positive potential with respect to said cathode.

2. An electric wave source comprising: a highvacuum electron discharge device having a cathode, an anode and a control electrode; a resonant circuit having a first terminal connected to said cathode and having a second terminal; a trans-- former having a plurality of windings; an electric energy source connected in series with one winding of said transformer between said second terminal of said resonant circuit and said anodefor producing electronic current through said device; and series-connected means including a resistance-capacitance circuit and a winding of said transformer coupling said control electrode to said second terminal of said resonant circuit, said control electrode being coupled to said electric energy source and biased thereby with respect to said cathode; whereby variations in the electronic current through said cathode and said anode induce voltage changes between said cathode and said control electrode to produce oscillations for exciting said resonant circuit.

RICHARD PROSKAUER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,919,985 Patterson July 25, 1933 1,923,252 Brolly Aug. 22, 1933 2,135,740 Urtel Nov. 8, 1938 2,179,607 Bedford Nov. 14, 1939 2,212,202 Faudell Aug. 20, 1940 2,277,000 Bingley Mar. 17, 1942 2,288,554 Smith June 30, 1942 2,292,835 Hepp Aug. 11, 1942 2,297,742 Campbell Oct. 6, 1942 2,364,756 Roberts Dec. 12, 1944 

